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Abstract:

A method and system for minimizing the control overhead in a
multi-carrier wireless communication network that utilizes a
time-frequency resource is disclosed. In some embodiments, one or more
zones in the time-frequency resource are designated for particular
applications, such as a zone dedicated for voice-over-IP (VoIP)
applications. By grouping applications of a similar type together within
a zone, a reduction in the number of bits necessary for mapping a packet
stream to a portion of the time-frequency resource can be achieved. In
some embodiments, modular coding schemes associated with the packet
streams may be selected that further reduce the amount of necessary
control information. In some embodiments, packets may be classified for
transmission in accordance with application type, QoS parameters, and
other properties. In some embodiments, improved control messages may be
constructed to facilitate the control process and minimize associated
overhead.

Claims:

1-36. (canceled)

37. A communication method for a mobile device in an orthogonal frequency
division multiple access (OFDMA) wireless packet system including a
plurality of base stations and mobile devices in a plurality of
geographic cells, each mobile device having an identifier that is
assigned by the system, the method comprising: receiving a signal over a
time-frequency resource region contained in a plurality of frames, the
signal carrying packets destined to a number of mobile devices with a
plurality of modulation and coding schemes using an integer multiple of
basic time-frequency resource units, wherein each frame is divided into a
plurality of time slots, each time slot consists of a plurality of
orthogonal frequency division multiplexing (OFDM) symbols, each OFDM
symbol contains a plurality of frequency subcarriers, and the basic
time-frequency resource unit contains a number of subcarriers in a number
of OFDM symbols; and identifying from the signal a plurality of packets
that are destined to the mobile device using a time index or a frequency
index of the time-frequency resource region in conjunction with the
identifier assigned to the mobile device.

42. The method of claim 37, wherein the identifier assigned to the mobile
device is released after a period of time.

43. The method of claim 37, wherein physical subcarrier and OFDM symbol
indices of a time-frequency resource are mapped to logical indices so
that the logical indices may be utilized by upper layer facilities in the
mobile device.

46. The method of claim 37, wherein one of the plurality of packets
destined to the mobile device is a control packet that carries a control
message for the mobile device.

47. The method of claim 46, wherein the control message comprises
information on modulation and coding schemes or resource allocation.

48. The method of claim 46, wherein the control packet uses a modulation
and coding scheme the same as or one level lower than modulation and
coding schemes used for other data packets that are destined to the
mobile device.

49. A communication method for a base station in an orthogonal frequency
division multiple access (OFDMA) wireless packet system including a
plurality of base stations and mobile devices in a plurality of
geographic cells, each mobile device having an identifier that is
assigned by the system, the method comprising: allocating a
time-frequency resource region in a plurality of frames for carrying
packets to a number of mobile devices with a plurality of modulation and
coding schemes using an integer multiple of basic time-frequency resource
units, wherein each frame is divided into a plurality of time slots, each
time slot consists of a plurality of orthogonal frequency division
multiplexing (OFDM) symbols, each OFDM symbol contains a plurality of
frequency subcarriers, and the basic time-frequency resource unit
contains a number of subcarriers in a number of OFDM symbols; generating
a plurality of packets for a mobile device in the system and scheduling
transmission of the plurality of packets in the time-frequency resource
region in a manner that allows the mobile device to recover the plurality
of packets using a time index or a frequency index of the time-frequency
resource region in conjunction with the identifier assigned to the mobile
device; and transmitting the plurality of packets to the mobile device.

54. The method of claim 49, wherein the identifier assigned to the mobile
device is released after a period of time.

55. The method of claim 49, further comprising mapping logical indices of
a time-frequency resource seen by upper layer facilities of the base
station to physical subcarrier and OFDM symbol indices prior to
transmitting the plurality of packets.

58. The method of claim 49, further comprising not using the same
time-frequency resource region that is used by a base station in an
adjacent cell.

59. In an orthogonal frequency division multiple access (OFDMA) wireless
packet system including a plurality of base stations in a plurality of
geographic cells, a mobile device having an identifier that is assigned
by the system, the mobile device comprising: a facility configured for
receiving a signal over a time-frequency resource region contained in one
or more frames, the signal carrying packets destined to a number of
mobile devices with a plurality of modulation and coding schemes using an
integer multiple of basic time-frequency resource units, wherein each
frame is divided into a plurality of time slots, each time slot consists
of a plurality of orthogonal frequency division multiplexing (OFDM)
symbols, each OFDM symbol contains a plurality of frequency subcarriers,
and the basic time-frequency resource unit contains a number of
subcarriers in a number of OFDM symbols; and a facility configured for
identifying from the signal a plurality of packets that are destined to
the mobile device using a time index or a frequency index of the
time-frequency resource region in conjunction with the identifier
assigned to the mobile device.

60. The mobile device of claim 59, wherein the time-frequency resource
region corresponds to a frame and the time index of the time-frequency
resource region corresponds to a frame number.

61. The mobile device of claim 59, wherein one of the plurality of
packets destined to the mobile device is a control packet that carries a
control message for the mobile device and the control message comprises
information on modulation and coding schemes or resource allocation.

62. The mobile device of claim 59, further comprising a facility for
synchronization, a facility for fast Fourier transform, a facility for
demodulation, a facility for channel estimation, and a facility for
channel decoding.

63. A base station in an orthogonal frequency division multiple access
(OFDMA) wireless packet system including a plurality of mobile devices in
a plurality of geographic cells, each mobile device having an identifier
that is assigned by the system, the base station comprising: a facility
configured for allocating a time-frequency resource region in one or more
frames for carrying packets to a number of mobile devices with a
plurality of modulation and coding schemes using an integer multiple of
basic time-frequency resource units, wherein each frame is divided into a
plurality of time slots, each time slot consists of a plurality of
orthogonal frequency division multiplexing (OFDM) symbols, each OFDM
symbol contains a plurality of frequency subcarriers, and the basic
time-frequency resource unit contains a number of subcarriers in a number
of OFDM symbols; a facility configured for generating a plurality of
packets for a mobile device in the system and scheduling transmission of
the plurality of packets in the time-frequency resource region in a
manner that allows the mobile device to recover the plurality of packets
using a time index or a frequency index of the time-frequency resource
region in conjunction with the identifier assigned to the mobile device;
and a transmitter configured for transmitting the plurality of packets to
the mobile device.

64. The base station of claim 63, wherein the time-frequency resource
region corresponds to a frame and the time index of the time-frequency
resource region corresponds to a frame number.

65. The base station of claim 63, wherein one of the plurality of packets
destined to the mobile device is a control packet that carries a control
message for the mobile device and the control message comprises
information on modulation and coding schemes or resource allocation.

66. The base station of claim 63, further comprising a facility for
channel encoding, a facility for modulation, and a facility for inverse
fast Fourier transform.

[0003] Bandwidth efficiency is one of the most important system
performance factors for wireless communication systems. In packet based
data communication, where the traffic has a bursty and irregular pattern,
application payloads are typically of different sizes and with different
quality of service (QoS) requirements. In order to accommodate different
applications, a wireless communication system should be able to provide a
high degree of flexibility. However, in order to support such
flexibility, additional overhead is usually required. For example, in a
wireless system based on the IEEE 802.16 standard ("WiMAX"), multiple
packet streams are established for each mobile station to support
different applications. At the medium access control (MAC) layer, each
packet stream is mapped into a wireless connection. The MAC scheduler
allocates wireless airlink resources to these connections. Special
scheduling messages, DL-MAP and UL-MAP, are utilized to broadcast the
scheduling decisions to the mobile stations.

[0004] In the MAP scheduling message defined by IEEE802.16, there is
significant control overhead. For example, each connection is identified
by a 16 bits connection ID (CID). The CID is included in the MAP message
to identify the mobile station. The maximum number of connections that a
system can support is therefore 65,536. Each mobile station has at least
two management connections for control and management messages and a
various number of traffic connections for application data traffic. As
another example, each connection includes the identification of an
airlink resource that can correspond to any time/frequency region that is
allocated for communication. The resource allocation is identified in the
time domain scale with a start symbol offset (8 bits) and a symbol length
(7 bits) and in the frequency domain scale with a start logical
subchannel offset (6 bits) and a number of allocated subchannels (6
bits). Due to the fact that different applications have different
resource requirements, the allocated resource region is irregular from
connection to connection. As a still further example, the modulation and
coding scheme for each connection is identified by a 4-bit MCS code,
identified as either a downlink interval usage code (DIUC) or an uplink
interval usage code (UIUC). Another 2 bits are used to indicate the
coding repetition in addition to 3 bits for power control. Overall, the
overhead of a MAP message is 52 bits. For applications such as
voice-over-IP (VoIP), the payload of an 8 Kbps voice codec is 20 bytes in
every 20 ms. The overhead of the MAP message alone can therefore account
for as much as 32.5% of the overall data communication, thereby resulting
in a relatively low spectral efficiency. It would therefore be beneficial
to reduce the overhead in a multi-carrier packet communication system to
improve the spectral efficiency of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 illustrates the coverage of a wireless communication network
that is comprised of a plurality of cells.

[0006] FIG. 2 is a block diagram of a receiver and a transmitter, such as
might be used in a multi-carrier wireless communication network.

[0007] FIG. 3 is a block diagram depicting a division of communication
capacity in a physical media resource.

[0008] FIG. 4 is a graphical depiction of the relationship between a
sampling frequency, a channel bandwidth, and usable subcarriers in a
channel.

[0009] FIG. 5 is a graphical depiction of the structure of a multi-carrier
signal in the frequency domain.

[0010] FIG. 6 is a block diagram of a time-frequency resource utilized by
a wireless communication network.

[0011] FIG. 7 is a block diagram of a classifier for classifying received
packets by application, QoS, or other factor.

[0012] FIGS. 8A and 8B are block diagrams of representative control
message formats.

[0013] FIG. 9 is a block diagram of a special resource zone with unit
sequence defined in time-first order.

[0014] FIGS. 10A-10C are block diagrams illustrating the reallocated of
resources within a resource zone.

DETAILED DESCRIPTION

[0015] A system and method for minimizing the control overhead in a
multi-carrier wireless communication network that utilizes a
time-frequency resource is disclosed. In some embodiments, one or more
zones in the time-frequency resource are designated for particular
applications, such as a zone dedicated for voice-over-IP (VoIP)
applications. By grouping applications of a similar type together within
a zone, a reduction in the number of bits necessary for mapping a packet
stream to a portion of the time-frequency resource can be achieved. In
some embodiments, modular coding schemes associated with the packet
streams may be selected that further reduce the amount of necessary
control information.

[0016] In some embodiments, packets may be classified for transmission in
accordance with application type, QoS parameters, and other properties.
An application connection-specific identifier (ACID) may also be assigned
to a packet stream. Both measures reduce the overhead associated with
managing multiple application streams in a communication network.

[0017] In some embodiments, improved control messages may be constructed
to facilitate the control process and minimize associated overhead. The
control messages may include information such as the packet destination,
the modulation and coding method, and the airlink resource used. Control
messages of the same application type or subtype, modulation and coding
scheme, or other parameter may be grouped together for efficiency.

[0018] While the following discussion contemplates the application of the
disclosed technology to an Orthogonal Frequency Division Multiple Access
(OFDMA) system, those skilled in the art will appreciate that the
technology can be applied to other system formats such as Code Division
Multiple Access (CDMA), Multi-Carrier Code Division Multiple Access
(MC-CDMA), or others. Without loss of generality, OFDMA is therefore only
used as an example to illustrate the present technology. In addition, the
following discussion uses voice-over-IP as a representative application
to which the disclosed technology can be applied. The disclosed
technology is equally applicable to other applications including, but not
limited to, audio and video.

[0019] The following description provides specific details for a thorough
understanding of, and enabling description for, various embodiments of
the technology. One skilled in the art will understand that the
technology may be practiced without these details. In some instances,
well-known structures and functions have not been shown or described in
detail to avoid unnecessarily obscuring the description of the
embodiments of the technology. It is intended that the terminology used
in the description presented below be interpreted in its broadest
reasonable manner, even though it is being used in conjunction with a
detailed description of certain embodiments of the technology. Although
certain terms may be emphasized below, any terminology intended to be
interpreted in any restricted manner will be overtly and specifically
defined as such in this Detailed Description section.

I. Wireless Communication Network

[0020] FIG. 1 is a representative diagram of a wireless communication
network 100 that services a geographic region. The geographic region is
divided into a plurality of cells 105, and wireless coverage is provided
in each cell by a base station (BS) 110. One or more mobile devices (not
shown) may be fixed or may roam within the geographic region covered by
the network. The mobile devices are used as an interface between users
and the network. Each base station is connected to the backbone of the
network, usually by a dedicated link. A base station serves as a focal
point to transmit information to and receive information from the mobile
devices within the cell that it serves by radio signals. Note that if a
cell is divided into sectors, from a system engineering point of view
each sector can be considered as a cell. In this context, the terms
"cell" and "sector" are interchangeable.

[0021] In a wireless communication system with base stations and mobile
devices, the transmission from a base station to a mobile device is
called a downlink (DL) and the transmission from a mobile device to a
base station is called an uplink (UL). FIG. 2 is a block diagram of a
representative transmitter 200 and receiver 205 that may be used in base
stations and mobile devices to implement a wireless communication link.
The transmitter comprises a channel encoding and modulation component
210, which applies data bit randomization, forward error correction (FEC)
encoding, interleaving, and modulation of an input data signal. The
channel encoding and modulation component is coupled to a subchannel and
symbol construction component 215, an inverse fast Fourier transform
(IFFT) component 220, and a radio transmitter component 225. Those
skilled in the art will appreciate that these components construct and
transmit a communication signal containing the data that is input to the
transmitter 200. Other forms of transmitter may, of course, be used
depending on the requirements of the communication network.

[0022] The receiver 205 comprises a reception component 230, a frame and
synchronization component 235, a fast Fourier transform component 240, a
frequency, timing, and channel estimation component 245, a subchannel
demodulation component 250, and a channel decoding component 255. The
channel decoding component de-interleaves, decodes, and derandomizes a
signal that is received by the receiver. The receiver recovers data from
the signal and outputs the data for use by the mobile device or base
station. Other forms of receiver may, of course, be used depending on the
requirements of the communication network.

[0023] FIG. 3 is a block diagram depicting the division of communication
capacity in a physical media resource 300 (e.g., radio or cable) into
frequency and time domains. The frequency is divided into two or more
subchannels 305, represented in the diagram as subchannels 1, 2, . . . m.
Time is divided into two or more time slots 310, represented in the
diagram as time slots 1, 2, . . . n. The canonical division of the
resource by both time and frequency provides a high degree of flexibility
and fine granularity for resource sharing between multiple applications
or multiple users of the resource.

[0024] FIG. 4 is a block diagram representing the relationship between the
bandwidth of a given channel and the number of usable subcarriers within
that channel. A multi-carrier signal in the frequency domain is made up
of subcarriers. In FIG. 4, the sampling frequency is represented by the
variable fs, the bandwidth of the channel is represented by the
variable Bch, and the effective bandwidth by the variable Beff
(where the effective bandwidth is a percentage of the channel bandwidth).
The number of usable subcarriers within the channel is defined by the
following equation:

# _usable _subcarriers = B eff f s × N fft
##EQU00001##

Where Nfft is the length of the fast Fourier transform. Those
skilled in the art will appreciate that for a given bandwidth of a
spectral band or channel (Bch), the number of usable subcarriers is
finite and limited, and depends on the size of the FFT, the sampling
frequency (fs), and the effective bandwidth (Beff) in
accordance with equation 1.

[0025] FIG. 5 is a signal diagram depicting the various subcarriers and
subchannels that are contained within a given channel. There are three
types of subcarriers: (1) data subcarriers, which carry information data;
(2) pilot subcarriers, whose phases and amplitudes are predetermined and
made known to all receivers, and which are used for assisting system
functions such as estimation of system parameters; and (3) silent
subcarriers, which have no energy and are used for guard bands and as a
DC carrier. The data subcarriers can be arranged into groups called
subchannels to support scalability and multiple-access. The subcarriers
forming one subchannel may or may not be adjacent to each other. Each
mobile device may use some or all of the subchannels.

[0026] A multi-carrier signal in the time domain is generally made up of
time frames, time slots, and OFDM symbols. A frame consists of a number
of time slots, and each time slot is comprised of one or more OFDM
symbols. The OFDM time domain waveform is generated by applying an
inverse-fast-Fourier-transform (IFFT) to the OFDM symbols in the
frequency domain. A copy of the last portion of the time domain waveform,
known as the cyclic prefix (CP), is inserted in the beginning of the
waveform itself to form an OFDM symbol.

[0027] In some embodiments, a mapper such as the subchannel and symbol
construction component 215 in FIG. 2 is designed to map the logical
frequency/subcarrier and OFDM symbol indices seen by upper layer
facilities, such as the MAC resource scheduler or the coding and
modulation modules, to the actual physical subcarrier and OFDM symbol
indices. A contiguous time-frequency area before the mapping may be
actually discontinuous after the mapping, and vice versa. On the other
hand, in a special case, the mapping may be a "null process", which
maintains the same time and frequency indices before and after the
mapping. The mapping process may change from time slot to time slot, from
frame to frame, or from cell to cell. Without loss of generality, the
terms "resource", "airlink resource", and "time-frequency resource" as
used herein may refer to either the time-frequency resource before such
mapping or after such mapping.

II. Airlink Resource Zones

[0028] Various technologies are now described that may be utilized in
conjunction with the wireless communication network 100 in order to
reduce the amount of control overhead associated with the use of system
resources. By reducing the control overhead, greater spectral efficiency
is achieved allowing the system to, among other benefits, maximize the
amount of simultaneously supported communications.

[0029] FIG. 6 is a map of a time-frequency resource 600 that is allocated
for use by the wireless communication network 100. As described above, in
a typical wireless system based on the IEEE 802.16 standard ("WiMAX"),
multiple packet streams are established for each mobile device to support
different applications. At the medium access control (MAC) layer, each
packet stream is mapped into a wireless connection. As a result, various
applications carried in packet streams may be spread throughout the
available time-frequency resource. To overcome the inefficiencies
associated with maintaining this mapping, FIG. 6 depicts an alternative
way of managing multiple packet streams. The time-frequency resource 600
may be divided into one or more zones 605a, 605b, . . . 605n. Each of the
zones 605a, 605b, . . . 605n is associated with a particular type of
application. For example, zone 605a may be associated with voice
applications (e.g., VoIP), zone 605b may be associated with video
applications, and so on. As will be described in additional detail below,
by grouping like applications together the amount of control overhead in
MAC headers is reduced. Zones may be dynamically allocated, modified, or
terminated by the system.

[0030] When applications of a similar type are grouped together within a
zone, a reduction in the number of bits necessary for mapping a packet
stream to a time-frequency segment can be achieved. In some embodiments,
the identification of the time-frequency segment associated with a
particular packet stream can be indicated by the starting time-frequency
coordinate and the ending time-frequency coordinate relative to the
starting point of the zone. The granularity in the time coordinates can
be one or multiple OFDM symbols, and that in the frequency coordinates
can be one or multiple subcarriers. If the time-frequency resource is
divided into two or more zones, the amount of control information
necessary to map to a location relative to the starting point of the zone
may be significantly less than the amount of information necessary to map
to an arbitrary starting and ending coordinate in the entire
time-frequency resource.

[0031] Within each zone 605a, 605b, . . . 605n, the time-frequency
resource may be further divided in accordance with certain rules to
accommodate multiple packet streams V1, V2, . . . Vm. For
example, as depicted in FIG. 6, zone 605a is divided into multiple
columns and the packet streams are arranged from top down in each column
and from left to right across the columns. The width of each column can
be a certain number of subcarriers. Each packet stream V1, V2,
. . . Vm may be associated with an application. For example, V1
is the resource segment to be used for the first voice packet stream,
V2 is the resource segment to be used for the second voice packet
stream, etc. While the zone 605a is divided and the packet streams
numbered starting at an origin of the zone, it will be appreciated that
the division of the time-frequency resource in accordance with certain
rules may start at other origin locations within the zone as well.
Segments within each zone may be dynamically allocated by the system as
requested and released by the system when expressly or automatically
terminated.

[0032] When the zones are further subdivided into time-frequency segments
in accordance with certain rules, a mapping of packet streams to segment
may be achieved using a one-dimensional offset with respect to the origin
of the zone rather than the two-dimensional (i.e. starting time-frequency
coordinate and ending time-frequency coordinate relative to the starting
point of the zone) mapping method discussed above. Calculation of such an
offset may require knowledge of a modulation and coding scheme that is
associated with a particular packet stream. For example, Table 1 below
sets forth representative modulation and forward-error correction (FEC)
coding schemes (MCS) that may be used for voice packet streams under
various channel conditions.

[0033] In some embodiments, the MCS may be selected to utilize modular
resources. For example, as illustrated in Table 1, 80 raw modulation
symbols are needed to transmit 160 information bits using 16QAM
modulation and rate-1/2 coding, the highest available MCS in the table.
The resource utilized by this highest MCS is called a basic resource unit
("Unit"), i.e., 80 raw symbols in this example. The resource utilized by
other MCS is simply an integer multiple of the basic unit. For example,
four units are required to transmit the same number of information bits
using QPSK modulation with rate-1/4 coding. The MCS index (MCSI) conveys
the information about modulation and coding schemes. For a known vocoder,
MCSI also implies the number of AMC resource units required for a voice
packet. Those skilled in the art will appreciate that coding and signal
repetition can be combined to provide lower coding rates. For example,
rate-1/8 coding can be realized by a concatenation of rate-1/2 coding and
4-time repetition.

[0034] The decision process for selecting the proper MCS of a packet can
vary by application. In some embodiments, the process for voice packets
can be more conservative than that for general data packets due to the
QoS requirements of the voice applications. For example, when the signal
to interference noise ratio (SINR) is used as a threshold for selecting
the MCS, the threshold value for voice packets is set higher than that
for general data packets. For example, the SINR threshold of QPSK with
rate-1/2 coding for voice packets is 12 dB, while that for general data
packets is 10 dB.

[0035] If a MCS from Table 1 is selected for each packet stream contained
in a particular zone, the offset to a segment representing a particular
packet stream may be easily calculated. For example, an index VZI1,
VZI2, . . . VZIm is shown at the origin of each segment that is
contained in the zone 605a. The index for any selected packet stream is
defined as the sum of all basic resource units associated with each
packet stream preceding the selected packet stream, with an optional
adjustment depending on the location where the division of the
time-frequency resource is started (typically no adjustment is required
since the division starts at the origin of the zone). For example, the
location index for the first voice packet stream is VZI1=0 since it
starts at the origin of the zone 605a. The first packet stream has an MCS
of 1, which implies that one basic resource unit is used. As a result,
the index for the second voice packet stream is VZI2=1. The second
packet stream has an MCS of 4, which implies that eight basic resource
units are used. As a result, the index for the third voice packet stream
is VZI3=9, arrived by summing the basic resource units used for the
preceding first and second packet streams.

[0036] Using basic resource units as the granularity of a location offset
to the packet stream reduces the number of bits required to represent its
location with the zone 605a. For example, to support a maximum of 64 VoIP
calls in a cell, a maximum of 64×8=512 units might be used,
assuming that every voice packet is transmitted using the lowest MCS.
Therefore, a 9-bit number is sufficient to represent a VZI. In practice,
different voice packets may be transmitted using different MCSs, some
with MCSI=1, some with MCSI=4, so on so forth. According to statistics, a
shorter bit-length than the maximum needed, for example 8 bits, may be
used for VZI for practical purpose.

[0037] In some embodiments, control information necessary to map a packet
stream to a resource segment may be still further reduced. In the case
where an MCS is used with packet streams that are located sequentially in
the zone. the index of a packet can be inferred from the MCSI of the
packets located before the subject packet. For example, if the first
voice packet stream uses MCSI1=1, 16QAM with 1/2 coding, and the
second voice packet stream uses MCSI2=4, QPSK with 1/8 coding, then
the first two voice packet streams occupy 1+8=9 units, and the starting
location of the third voice packet stream is the 9th unit. Rather than
encode the index for each packet stream in the control information, the
index can be omitted in the control message and the offset from the
origin of the zone calculated as necessary.

[0038] Allocation of the time-frequency resource 600 can be carried out in
a variety of ways. In some embodiments, an application zone may contain
all subcarriers of one or multiple OFDM symbols or time slots. In some
embodiments, the definition of an application zone, such as the location
and size of the zone, may be different from cell-to-cell 105. In some
embodiments, in order to avoid inter-cell interference the zones of
similar applications are allocated at different locations in neighboring
cells. For example, voice applications may be located at a lower
frequency range in the time-frequency resource in one cell, and at a
higher frequency range in the time-frequency range in an adjacent cell.
In some embodiments, the system allocates a fixed amount of resource to
each voice connection. The system uses AMC and matches it with adaptive
multi-rate (AMR) voice coding to improve the voice quality. Moreover,
unused resources in one application zone may be allocated for other
applications.

[0039] In a system with one or multiple application zones, the remaining
resource unused by the application zones can be treated as a special
resource zone. The special resource zone may be irregular in shape. For
example, FIG. 9 depicts a time-frequency resource 900 having three
defined zones 905, 910, and 915. The remaining resource area that is
shaded in the figure represents the special resource zone. The MAC
scheduler may track the time-frequency resources in this special zone and
broadcast the resource allocation in a special zone MAP message. In some
embodiments, the special zone MAP message explicitly identifies the
resource zone, for example using the time and frequency coordinates of a
resource block. A mobile device can identify its own resource by decoding
the MAP message.

[0040] In some embodiments, both the base station and the mobile device
share the configuration information of the special resource zone, and
view the special zone as a contiguous resource zone. The MAP message only
includes the resource allocation information in the special resource
zone, using connection ID (described below), resource identification
parameters and MCS index.

[0041] In some embodiments, the MAP message can be further compressed if
the special resource zone is further divided into a sequence of
pre-defined resource units. For example, the shaded area in FIG. 9 has
been further divided into forty-two resource units 920, first numbered
sequentially along the time axis and then continuing in columns along the
frequency axis. If the size of each resource unit is pre-defined, the
location within the special resource zone may be determined based on a
mapping to a sequence number.

III. Application Connection IDs

[0042] When a mobile device enters a wireless network, it is first
assigned a basic connection identification (BCID) for each direction of
the wireless connection: downlink and uplink. A BCID can be used for
control messages or generic (unclassified) application connections. The
BCID for downlink may or may not be the same as that of the uplink.

[0043] In some embodiments, a classification of packet streams may be
performed by the system. FIG. 7 is a block diagram of a system component
700 for receiving IP packets and sorting the received packets into
various streams. The system component 700 includes a classifier 705
having associated classification rules 710. The classifier receives
incoming packets, each packet having various header information such as
an Ethernet header 715, an IP header 720, a UDP header 725, an RTP header
730 and an RTP payload 735. The packets are classified by the classifier
705 and output into different application data queues 740 where they will
subsequently be transmitted by an OFDMA transmitter 745.

[0044] The classifier 705 is able to classify the packets based on
application type, quality of service (QoS) requirement, or other
properties. For example, packets from a voice application stream are
identified based on a special value in the type of service (ToS) field in
the IP header 720 of the packets. A new combination of RTP/UDP/IP headers
with the special IP ToS field value indicates a new voice application
stream. Such a new stream is identified by peeking into voice session
setup protocol messages, such as session initiation protocol (SIP). The
classification performed by the classifier is based on one or more
classification rules 710. The classification rules can be configured
statically or dynamically by a control process. Each classification rule
is defined using parameters, such as application type, QoS parameters,
and other properties that may be determined from the received packets.

[0045] In some embodiments, the incoming packets may also be assigned an
application connection-specific identifier (ACID) in addition to or in
lieu of a BCID. Each ACID can be assigned to a corresponding packet
stream. For example, an ACID can be assigned to voice packets that
together make up a voice application. When an ACID is assigned to a voice
application, the ACID may also be referred to as a voice connection ID
(VCID). As another example, an ACID can be assigned to a packet stream
that requires a particular QoS. Furthermore, an application packet stream
can be further classified into different sub-types, based on certain
properties of that application. For example, voice applications can be
further classified into different sub-types based on the voice source
coding (vocoder) methods (e.g., G.711 and G.729A). When further
classified in this matter, the sub-types may each be assigned their own
ACID. For certain multi-casting applications, an ACID may also be shared
by multiple base stations or mobile devices.

[0046] Once established, the connection IDs, including BCIDs and ACIDs,
are disseminated, through broadcasting messages for example, to the
corresponding base station(s) and mobile device(s) for proper packet
transmission and reception. As was previously discussed, the medium
access control (MAC) scheduler may allocate specific zones of airlink
resources for certain types of packet streams.

[0047] A connection ID is released once the wireless system determines
that there is no need to continue the connection. For example, a voice
connection and its VCID are released once the system detects deactivation
of the voice stream. In some embodiments, the voice connection is
deactivated if the voice session disconnect is detected through snooping
SIP signaling. In some embodiments, the voice connection is released if
there is no voice packet activity on the connection for a certain period
of time.

[0048] In some embodiments, the same bit length is used in different types
of connections IDs, including BCIDs and ACIDs. In some embodiments,
different types of connection IDs may have different bit lengths. For
example, in a typical implementation for voice applications, a BCID may
be 16-bits to accommodate a large number of mobile devices and
unclassified applications, while a VCID is 6-bits to accommodate up to 64
simultaneous voice connections in a cell. A shorter ACID length is
beneficial for reducing control overhead, especially when an application
utilizes many small data packets, such as VoIP packets.

[0049] In some embodiments, an ACID is further augmented by other
properties of the utilized airlink resources, such as time or frequency
indices, to identify an application connection. This can be used to
further reduce ACID bit length or to increase the maximum number of
accommodated application connections given a certain ACID bit length. For
example, a voice codec generates voice application data periodically. The
allocation period is usually a multiple of the airlink frame duration. In
this case, the airlink frame number can be combined with a VCID to
identify a voice connection. For example, the voice codec of G.723.1
generates a voice frame once every 30 milliseconds. The MAC scheduler
allocates airlink resource to such a voice connection once every 30 ms.
In a wireless cellular system using 5 ms frame duration, a single VCID
can be shared by 6 voice streams, each associated with a different frame
number to uniquely identify a voice connection.

IV. Control Messages

[0050] When airlink resource zones or application-specific IDs are
utilized by the system, various improved control messages, often called
Information Elements (IEs), may be constructed to facilitate the control
process and minimize the control overhead. Various control message
improvements are described herein.

[0051] In some embodiments, the IE is sent prior to transmitting an
application packet to indicate information associated with the packet,
such as the packet destination, the modulation and coding method, and the
airlink resource used. For example, the IE for a voice packet may include
the VCID (indicative of the packet destination), the MCSI (encoding
scheme), and the VZI (index to location of the packet stream within the
airlink resource). In some embodiments, the VCID is 6 bits, the MCSI is 2
bits, and the VZI is 8 bits, thereby resulting in a 2-byte IE overhead
for each voice packet. Alternatively, the IE for a voice packet may
include only the VCID and the MCSI, with the VZI inferred from the MCSIs
of previous packet streams in the airlink resource as described above.
When using only the VCID and MCSI, the IE overhead for each voice packet
is reduced to only 1 byte. Additional control information, such as power
control information, can be added to the IE with additional bit fields.
The reduction in control bits improves the overall bandwidth efficiency
of the wireless communication network.

[0052] In some embodiments, a base station sends the IE before a downlink
packet to inform the mobile device for proper reception of the packet,
and the base station sends the IE before an uplink packet to inform the
mobile device for proper transmission of the packet. The downlink and
uplink packet IEs may be separately grouped together. The IEs may be
broadcasted or multi-casted to corresponding destinations.

[0053] In some embodiments, the IEs of the same application type or
subtype may be grouped together. A special field, called an Application
MAP (AMAP) subheader, for a specific application type, may be added to
the IE. The subheader may indicate the application type and the length of
the IE group. FIG. 8A is a block diagram of a representative IE 800 with
an AMAP subheader 805, in this case used for voice applications. The AMAP
subheader 805 includes a type variable and a length variable. As depicted
in FIG. 8A, type=01 indicates that the application type is voice.
Length=3 indicates that the subheader is followed by three voice IEs. The
remainder of the IE contains the three voice IEs 810a, 810b, and 810c.
For example, if the AMAP subheader was associated with streams in the
zone 605a depicted in FIG. 6, then voice IE 810a would pertain to packet
stream V1, voice IE 810b would pertain to packet stream V2, and
voice IE 810c would pertain to packet stream V3. Those skilled in
the art will appreciate that the although text is used to indicate the
contents of the IE in FIG. 8A, in an actual implementation the text would
be replaced by appropriately coded information.

[0054] In some embodiments, the IEs for all packets that are transmitted
with the same modulation and coding schemes (MCS) are grouped together
for efficiency. FIG. 8B is a block diagram of a block 850 of IEs that are
grouped by MCS. A frame control header (FCH) 855 or other control message
is transmitted prior to the block to indicate the length and the MCS used
for each segment of the block. In some embodiments, adaptive modulation
and coding (AMC) is used for the transmission of the IE's. A special
rule, which is known to both base stations and mobile devices, can be
used to determine the IE MCS, based on the MCS of its corresponding
packet for proper reception of the IE. In some embodiments, the MCS for
an IE is maintained the same as that of its corresponding application
packet. In some embodiments, the MCS for an IE is one level more
conservative than that of its corresponding packet. For example, if the
MCSI for a packet is 2 (QPSK with rate-1/2 coding), then the MCSI for its
IE is 3 (QPSK with rate-1/4 coding).

V. Voice Activity Detection

[0055] Typical voice conversations contain approximately 50 percent
silence. In order to take advantage of the fact that about half of the
time data does not need to be transmitted at the same rate as when a user
is speaking, the system may rely upon detecting the period of silence and
reducing the effective data transfer rate during that period. The silence
period in conversation is detected by a vocoder using technologies such
as Voice Activity Detection (VAD). Voice packets are only generated when
voice activity is detected. During the silence period, the voice packet
data rate is greatly reduced.

[0056] In addition to reducing the voice packet data rate during periods
of silence, the bandwidth allocation for the voice connection may also be
reduced. The MAC scheduler at the base station may use the indication of
voice activity to adjust the bandwidth allocation for the voice
connection. In the uplink direction, the mobile device sends a special
MAC message once a VAD indication is received from its vocoder. The MAC
message indicates to the base station that the voice data rate is being
temporarily reduced. When such an indication is received, the MAC
scheduler can reduce the airlink resource allocated to the voice
connection. Similarly, if the VAD indicates new voice activity, the
mobile device notifies the base station using a MAC message and the
original resource allocation is re-applied to the voice connection.

[0057] In the downlink direction, if there is no voice packet to be
transmitted over a voice connection, the MAC scheduler allocates the
resource to other voice connections. As a consequence, a resource block
previous allocated for the connection in a particular zone may become
vacant. Several methods can be used to deal with such fragmentation in
the zone.

[0058] In some embodiments, the MAC scheduler at the base station
reallocates the resource with the objective of minimizing the impact to
other voice connections, such as their adaptive modulation and coding
processes.

[0059] In some embodiments, the MAC scheduler maintains the resource
allocation of the other voice connections, and allocates the resource
vacated by the silent voice connection to new voice connections or other
application packets.

[0060] In some embodiments, the MAC scheduler moves all the subsequent
allocations up to fill the resource gap. As shown in FIG. 10A, once a
voice connection, identified by VCID 2 enters a silent period, the other
voice connections are moved by the MAC scheduler to occupy the resource
vacated by VCID 2.

[0061] In some embodiments, the MAC scheduler uses the last voice
time-frequency resource in the same zone to fill the resource gap of a
silent voice connection. FIG. 10B illustrates such a case, when the MAC
scheduler moves the last voice connection VCID 12 to occupy the resource
allocation gap that is vacated by the voice connection VCID 2.

[0062] In some embodiments, the MAC scheduler uses the last voice
time-frequency resource that has the same coding and modulation scheme,
and is contained in the same zone, to fill the resource gap. The resource
gap that is introduced by such a replacement is then filled by the voice
time-frequency resource that is subsequent to the voice time-frequency
resource that was moved. As shown in FIG. 10C, voice connection VCID 6
uses the same coding and modulation scheme as voice connection VCID 2,
and is the last connection having that scheme in the zone. When voice
connection VCID 2 goes into a silent period, the MAC scheduler allocates
the voice connection VCID 2 resource to voice connection VCID 6. The MAC
scheduler then moves resources after voice connection VCID 6,
specifically VCID 7 in FIG. 10C, to occupy the resource allocation gap
that is caused by moving voice connection VCID 6.

[0063] The above detailed description of embodiments of the system is not
intended to be exhaustive or to limit the system to the precise form
disclosed above. While specific embodiments of, and examples for, the
system are described above for illustrative purposes, various equivalent
modifications are possible within the scope of the system, as those
skilled in the relevant art will recognize. For example, while processes
are presented in a given order, alternative embodiments may perform
routines having steps in a different order, and some processes may be
deleted, moved, added, subdivided, combined, and/or modified to provide
alternative or subcombinations. Each of these processes may be
implemented in a variety of different ways. Further any specific numbers
noted herein are only examples: alternative implementations may employ
differing values or ranges.

[0064] These and other changes can be made to the invention in light of
the above Detailed Description. While the above description describes
certain embodiments of the technology, and describes the best mode
contemplated, no matter how detailed the above appears in text, the
invention can be practiced in many ways. Details of the system may vary
considerably in its implementation details, while still being encompassed
by the technology disclosed herein. As noted above, particular
terminology used when describing certain features or aspects of the
technology should not be taken to imply that the terminology is being
redefined herein to be restricted to any specific characteristics,
features, or aspects of the technology with which that terminology is
associated. In general, the terms used in the following claims should not
be construed to limit the invention to the specific embodiments disclosed
in the specification, unless the above Detailed Description section
explicitly defines such terms. Accordingly, the actual scope of the
invention encompasses not only the disclosed embodiments, but also all
equivalent ways of practicing or implementing the invention under the
claims.

Patent applications by Haiming Huang, Bellevue, WA US

Patent applications by Ruifeng Wang, Sammamish, WA US

Patent applications by Titus Lo, Bellevue, WA US

Patent applications by Xiaodong Li, Kirkland, WA US

Patent applications in class Having both time and frequency assignment

Patent applications in all subclasses Having both time and frequency assignment